The basic purpose for traffic speed enforcement is to promote the orderly movement of traffic at an expeditious, and yet safe rate of speed. Commonly available commercial systems, such as radar and vascar provide information to police officers as to speed of vehicle operation, and are useful in making and supporting arrests of drivers of vehicles that are traveling too fast.
The mere presence of a police car equipped with radar or vascar tends to slow traffic, and often slows it to an inefficient velocity. Arrests are almost always resented, and there is some question whether such resentment enhances traffic speed enforcement, or simply causes the driver to be determined not to get caught again. In addition, such systems are expensive to purchase and to operate, and must be monitored constantly to be effective.